Multi-gain signal amplifier with switchable amplifier architectures

ABSTRACT

Disclosed herein are signal amplifiers having a plurality of amplifier cores. Individual amplifier cores can be designed for particular gain modes to enhance particular advantages while reducing other disadvantages. The signal amplifier can then switch between amplifier cores when switching gain modes to achieve desired performance characteristics (e.g., improving noise figure or linearity). Examples of signal amplifiers disclosed herein include amplifier architectures with a high gain amplifier core that reduces the noise figure and a linearity boost amplifier core that increases linearity (e.g., for lower gain modes). The disclosed signal amplifiers can also have switchable reference biases to provide targeted bias current matching. The disclosed signal amplifiers can also include degeneration switching blocks for individual amplifier cores to improve signal linearity.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.62/437,052 filed Dec. 20, 2016 and entitled “MULTI-GAIN SIGNAL AMPLIFIERWITH SWITCHABLE AMPLIFIER ARCHITECTURES,” which is expresslyincorporated by reference herein in its entirety for all purposes.

BACKGROUND Field

The present disclosure relates to amplifiers for wireless communicationapplications.

Description of Related Art

Wireless communication devices typically include components in afront-end module that are configured to amplify received radio-frequency(RF) signals. The front-end module can include a plurality of gain modesto provide different levels of amplification.

SUMMARY

According to a number of implementations, the present disclosure relatesto a variable-gain signal amplifier configured to provide a plurality ofgain modes. The amplifier includes an input node configured to receivean input signal and an output node configured to provide an amplifiedoutput signal. The amplifier also includes a first active coreconfigured to receive the input signal and to generate the amplifiedoutput signal for the output node and a second active core configured toreceive the input signal and to generate the amplified output signal forthe output node. The amplifier also includes a gain mode selectorconfigured to direct the input signal to the first active core in afirst gain mode and to direct the input signal to the second active corein a second gain mode different from the first gain mode.

In some embodiments, the input signal comprises a radio frequencysignal. In some embodiments, the amplifier further includes a switchablereference bias circuit configured to provide a first reference biascurrent to the first active core in the first gain mode and a secondreference bias current to the second active core in the second gainmode. In some embodiments, the gain mode selector is configured toselectively provide a bypass path that bypasses the first active coreand the second active core and an amplification path that passes througheither the first active core or the second active core.

In some embodiments, the amplifier further includes a degenerationswitching block coupled to the first active core and to the secondactive core, the degeneration switching block configured to providetailored impedances to the first active core and to the second activecore. In further embodiments, the tailored impedances are configured toprovide improved linearity in the amplified output signal relative to avariable gain stage that is not coupled to the degeneration switchingblock with the tailored impedances. In further embodiments, thedegeneration switching block is configured to provide a first tailoredimpedance for the first gain mode and a second tailored impedance forthe second gain mode. In yet further embodiments, the first tailoredimpedance is greater than the second tailored impedance and the firstgain level is less than the second gain level.

In some embodiments, the amplifier further includes a control circuitconfigured to generate an amplification control signal to control thegain mode selector. In some embodiments, the first active core isconfigured to have a lower noise figure than the second active core. Infurther embodiments, the second active core is configured to have ahigher linearity than the first active core. In yet further embodiments,the first gain mode is higher than the second gain mode.

In some embodiments, the amplifier further includes a plurality of inputnodes. In further embodiments, the amplifier is configured to receive aplurality of input signals at the plurality of input nodes, individualreceived signals having frequencies within different signal frequencybands. In yet further embodiments, the amplifier is configured toamplify signals received at individual input ports independent ofamplification of other received signals.

In some embodiments, the amplifier further includes a bypass blockcoupled to the input node and configured to be activated in a low gainmode to provide a bypass path that does not include the first activecore and the second active core. In some embodiments, each of the firstactive core and the second active core include a cascode buffer coupledto an output of a gain stage.

According to a number of implementations, the present disclosure relatesto a front-end module that includes a packaging substrate and a variablegain signal amplifier implemented on the packaging substrate. Thevariable gain signal amplifier includes a first active core configuredto receive an input signal and to generate an amplified output signal, asecond active core configured to receive the input signal and togenerate the amplified output signal, a gain mode selector configured todirect the input signal to the first active core in a first gain modeand to direct the input signal to the second active core in a secondgain mode. The front-end module also includes a controller implementedto control the variable gain signal amplifier to provide a plurality ofgain modes including the first gain mode and the second gain mode.

In some embodiments, the variable gain signal amplifier further includesa degeneration switching block configured to provide tailored impedancesto the first active core and to the second active core. In someembodiments, the gain signal amplifier further includes a switchablereference bias circuit configured to provide independent bias currentsto the first active core and to the second active core. In someembodiments, the first active core is configured to have a lower noisefigure than the second active core and the second active core isconfigured to have a higher linearity than the first active core.

According to a number of implementations, the present disclosure relatesto a wireless device that includes an antenna, a filter assembly coupledto the antenna to receive signals and to direct frequency bands alongselect paths, and a variable gain signal amplifier. The variable gainsignal amplifier includes a first active core configured to receive aninput signal and to generate an amplified output signal, a second activecore configured to receive the input signal and to generate theamplified output signal, and a gain mode selector configured to directthe input signal to the first active core in a first gain mode and todirect the input signal to the second active core in a second gain mode.The wireless device also includes a controller implemented to controlthe variable gain signal amplifier to provide a plurality of gain modes.

In some embodiments, the device further includes a degenerationswitching block configured to provide tailored impedances to the firstactive core and to the second active core. In some embodiments, the gainsignal amplifier further includes a switchable reference bias circuitconfigured to provide independent bias currents to the first active coreand to the second active core. In some embodiments, the first activecore is configured to have a lower noise figure than the second activecore and the second active core is configured to have a higher linearitythan the first active core.

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features have been described herein. It is to be understoodthat not necessarily all such advantages may be achieved in accordancewith any particular embodiment. Thus, the disclosed embodiments may becarried out in a manner that achieves or optimizes one advantage orgroup of advantages as taught herein without necessarily achieving otheradvantages as may be taught or suggested herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example wireless device having a primary antennaand a diversity antenna with signal amplifiers having a plurality ofswitchable amplifier cores.

FIG. 2 illustrates an example diversity receiver (DRx) configurationincluding a DRx front-end module (FEM) that has a signal amplifier witha high linearity core and a low noise figure core.

FIGS. 3A, 3B, 3C, 3D, 3E, and 3F illustrate various example variablegain amplifier configurations that include a switchable reference bias,a gain mode selector, a bypass block, one or more degeneration switchingblocks, and a plurality of amplifier architectures configured to receiveinput signals and to selectively amplify the received signals with aselected amplifier architecture or to provide a bypass path through thebypass block.

FIG. 4 illustrates a variable-gain signal amplifier that includes aplurality of active cores in a variable-gain stage configured to receivean input signal and to generate an amplified output signal.

FIG. 5 illustrates a variable-gain signal amplifier that includes aswitchable reference bias coupled to the active cores of thevariable-gain stage.

FIG. 6 illustrates a variable-gain signal amplifier that includes abypass block that provides a bypass path in addition to theamplification path through one of the active cores of the variable-gainstage.

FIG. 7 illustrates a variable-gain signal amplifier that includes adegeneration switching block coupled to active cores of thevariable-gain stage.

FIG. 8A illustrates an example variable gain amplifier configurationthat is configured similarly to the variable gain amplifier of FIG. 3E.

FIG. 8B illustrates a switchable reference bias circuit used inconjunction with the amplifier configuration of FIG. 8A.

FIG. 9A illustrates another example amplifier configuration that issimilar to the amplifier configuration described herein with referenceto FIG. 8A with the inclusion of an inductor coupled to the multi-inputgain stage.

FIG. 9B illustrates another example amplifier configuration that adds avariable attenuator in the second active core relative to the amplifierconfiguration of FIG. 9A.

FIGS. 10A, 10B, 10C, 10D, and 10E illustrate examples of operating modesof the variable gain signal amplifier configuration of FIG. 9A.

FIGS. 11A, 11B, 11C, and 11D illustrate operation of a switchablereference bias circuit in different gain modes for signals fromdifferent inputs.

FIG. 12 illustrates that in some embodiments, some or all of theamplifier configurations, including some or all of the amplifierconfigurations having the combinations of features described herein, canbe implemented, wholly or partially, in a module.

FIG. 13 illustrates an example wireless device having one or moreadvantageous features described herein.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

The headings provided herein, if any, are for convenience only and donot necessarily affect the scope or meaning of the claimed invention.

Overview

Signal amplifiers in wireless devices, such as low noise amplifiers(LNAs), can be designed to amplify signals while providing desiredcharacteristics, such as a targeted noise figure (NF) or targetedlinearity. However, where a wireless device is designed to provide aplurality of gain modes, the signal amplifiers may suffer from reducedperformance in one or more of the gain modes to achieve desiredcharacteristics across the plurality of gain modes. Accordingly,disclosed herein are signal amplifiers that include a plurality ofswitchable amplifier architectures so that particular gain modes can usededicated amplifier architectures to provide desired characteristics forthose gain modes, such as low noise figure or high linearity.

Rather than providing a single amplifier core or architecture for allgain modes, the disclosed signal amplifiers provide a plurality ofamplifier cores allowing individual amplifier cores to be designed forparticular gain modes to achieve desired characteristics or to enhanceparticular advantages while reducing other disadvantages. For example,an amplifier architecture for high gain modes can be designed with afocus on achieving a targeted noise figure. As another example, anamplifier architecture for low gain modes can be designed with a focuson achieving a targeted linearity. The signal amplifier can then switchbetween using the high gain mode amplifier core (or the low NF core) forhigh gain modes, and the low gain amplifier core (or the high linearitycore) for low gain modes. In certain implementations, the amplifier coredesigned to achieve high linearity can include a switchable degenerationblock to further improve signal linearity.

One advantage of the disclosed amplifiers with switchable amplifiercores is that such a configuration allows for gain modes to beselectively directed to targeted amplifier architectures to achievedesired characteristics. This may change during operation of thewireless device so that while operating in a particular gain modesignals can be directed to a first active core during a first timeperiod to achieve a particular set of advantages, and while operating inthe same gain mode signals can be directed to a second active coreduring a second time period to achieve a different (possiblyoverlapping) set of advantages.

In some embodiments, the amplifiers disclosed herein can also beconfigured to receive multiple inputs and route the signals toappropriate amplifier architectures. In some embodiments, the signalamplifiers disclosed herein can perform multi-input processing withoutusing a switch between inputs. In some embodiments, the amplifiersdisclosed herein can be configured to achieve a desired or targeted biascurrent matching by using a switchable reference bias core. In someembodiments, the signal amplifiers disclosed herein can improve gainmode performance through the use of individual input matching per activecore.

FIG. 1 illustrates an example wireless device 100 having a primaryantenna 160 and a diversity antenna 170. The wireless device 100includes an RF module 106 and a transceiver 104 that may be controlledby a controller 102. The transceiver 104 is configured to convertbetween analog signals (e.g., radio-frequency (RF) signals) and digitaldata signals. To that end, the transceiver 104 may include adigital-to-analog converter, an analog-to-digital converter, a localoscillator for modulating or demodulating a baseband analog signal to orfrom a carrier frequency, a baseband processor that converts betweendigital samples and data bits (e.g., voice or other types of data), orother components.

The RF module 106 is coupled between the primary antenna 160 and thetransceiver 104. Because the RF module 106 may be physically close tothe primary antenna 160 to reduce attenuation due to cable loss, the RFmodule 106 may be referred to as a front-end module (FEM). The RF module106 may perform processing on an analog signal received from the primaryantenna 160 for the transceiver 104 or received from the transceiver 104for transmission via the primary antenna 160. To that end, the RF module106 may include filters, power amplifiers, low noise amplifiers, bandselect switches, attenuators, matching circuits, and other components.

When a signal is transmitted to the wireless device 100, the signal maybe received at both the primary antenna 160 and the diversity antenna170. The primary antenna 160 and diversity antenna 170 may be physicallyspaced apart such that the signal at the primary antenna 160 anddiversity antenna 170 is received with different characteristics. Forexample, in one embodiment, the primary antenna 160 and the diversityantenna 170 may receive the signal with different attenuation, noise,frequency response, and/or phase shift. The transceiver 104 may use bothof the signals with different characteristics to determine data bitscorresponding to the signal. In some implementations, the transceiver104 selects from between the primary antenna 160 and the diversityantenna 170 based on the characteristics, such as selecting the antennawith the highest signal-to-noise ratio. In some implementations, thetransceiver 104 combines the signals from the primary antenna 160 andthe diversity antenna 170 to increase the signal-to-noise ratio of thecombined signal. In some implementations, the transceiver 104 processesthe signals to perform multiple-input/multiple-output (MiMo)communication.

In some embodiments, the diversity antenna 170 is configured to receivesignals within multiple cellular frequency bands and/or wireless localarea network (WLAN) frequency bands. In such embodiments, the wirelessdevice 100 can include a multiplexer, switching network, and/or filterassembly coupled to the diversity antenna 170 that is configured toseparate the diversity signal into different frequency ranges. Forexample, the multiplexer can be configured to include a low pass filterthat passes a frequency range that includes low band cellularfrequencies, a bandpass filter that passes a frequency range thatincludes low band WLAN signals and mid-band and high-band cellularsignals, and a high pass filter that passes a frequency range thatincludes high-band WLAN signals. This example is merely for illustrativepurpose. As another example, the multiplexer can have a variety ofdifferent configurations such as a diplexer that provides thefunctionality of a high pass filter and a low pass filter.

Because the diversity antenna 170 is physically spaced apart from theprimary antenna 160, the diversity antenna 170 can be coupled to thetransceiver 104 by a transmission line, such as a cable or a printedcircuit board (PCB) trace. In some implementations, the transmissionline is lossy and attenuates the signal received at the diversityantenna 170 before it reaches the transceiver 104. Thus, in someimplementations, gain is applied to the signal received at the diversityantenna 170. The gain (and other analog processing, such as filtering)may be applied by the diversity receiver module 108. Because such adiversity receiver module 108 may be located physically close to thediversity antenna 170, it may be referred to a diversity receiverfront-end module.

The RF module 106 and the diversity receiver module 108 includerespective variable gain amplifiers 110 a, 110 b configured to provide aplurality of gain modes to amplify signals from the primary antenna 160and the diversity antenna 170, respectively. The variable gainamplifiers 110 a, 110 b can include a plurality of amplifierarchitectures 120. Individual amplifier architectures 120 can beactivated by the variable gain amplifier 110 a, 110 b based at least inpart on an operating gain mode. The activated amplifier architecture canbe designed to provide targeted or desired characteristics for theparticular gain mode(s) directed to the architecture. In this way,desired characteristics can be enhanced for individual gain modes.Signals received at the variable gain amplifiers 110 a, 110 b can beamplified using a particular amplifier architecture selected by thevariable gain amplifier 110 a, 110 b, or the signals can be allowed tobypass the amplifier architectures 120, as described in greater detailherein. The selected amplifier architecture 120, the bypass path, and/orthe gain mode of the variable gain amplifier 110 a, 110 b can becontrolled by the controller 102. The variable gain amplifier 110 a, 110b can receive multiple input signals and output a single signal or aplurality of output signals.

Advantageously, the architecture of the variable gain amplifier 110 a,110 b can provide for multi-input processing without the use of aswitch. The variable gain amplifier 110 a, 110 b can advantageouslyachieve targeted or improved linearity by using a dedicated amplifierarchitecture with tailored electrical properties. Similarly, thevariable gain amplifier 110 a, 110 b can advantageously achieve targetedor improved NF by using a dedicated amplifier architecture with tailoredelectrical properties. The variable gain amplifier 110 a, 110 b canprovide targeted or improved input to output isolation through the useof a shunt switch in a bypass path and/or in one or more of theamplifier architectures 120.

The controller 102 can be configured to generate and/or send controlsignals to other components of the wireless device 100. In someembodiments, the controller 102 provides signals based at least in parton specifications provided by the mobile industry processor interfacealliance (MIPI® Alliance). The controller 102 can be configured toreceive signals from other components of the wireless device 100 toprocess to determine control signals to receive to other components. Insome embodiments, the controller 102 can be configured to analyzesignals or data to determine control signals to send to other componentsof the wireless device 100. The controller 102 can be configured togenerate control signals based on gain modes provided by the wirelessdevice 100. For example, the controller 102 can send control signals tothe variable gain amplifiers 110 a, 110 b to control the gain mode.Similarly, the controller 102 can be configured to generate controlsignals to select amplifier architectures 120 to activate for particulargain modes. The controller 102 can be configured to generate controlsignals to control the variable gain amplifier 110 a, 110 b to provide abypass path.

In some implementations, the controller 102 generates amplifier controlsignal(s) based on a quality of service metric of an input signalreceived at the input. In some implementations, the controller 102generates the amplifier control signal(s) based on a signal receivedfrom a communications controller, which may, in turn, be based on aquality of service (QoS) metric of the received signal. The QoS metricof the received signal may be based, at least in part, on the diversitysignal received on the diversity antenna 170 (e.g., an input signalreceived at the input). The QoS metric of the received signal may befurther based on a signal received on a primary antenna 160. In someimplementations, the controller 102 generates the amplifier controlsignal(s) based on a QoS metric of the diversity signal withoutreceiving a signal from the communications controller. In someimplementations, the QoS metric includes a signal strength. As anotherexample, the QoS metric may include a bit error rate, a data throughput,a transmission delay, or any other QoS metric. In some implementations,the controller 102 controls the gain (and/or current) of the amplifiersin the variable gain amplifiers 110 a, 110 b. In some implementations,the controller 102 controls the gain of other components of the wirelessdevice 100 based at least in part on an amplifier control signal.

The variable gain amplifiers 110 a, 110 b may include a step-variablegain amplifier configured to amplify received signals with a gain of oneof a plurality of configured amounts indicated by an amplifier controlsignal. In some implementations, the variable gain amplifiers 110 a, 110b may include a continuously-variable gain amplifier configured toamplify received signals with a gain proportional to or dictated by theamplifier control signal. In some implementations, the variable gainamplifiers 110 a, 110 b may include a step-variable current amplifierconfigured to amplify received signals by drawing a current of one ofplurality of configured amounts indicated by the amplifier controlsignal. In some implementations, the variable gain amplifiers 110 a, 110b may include a continuously-variable current amplifier configured toamplify received signals by drawing a current proportional to theamplifier control signal.

FIG. 2 illustrates an example diversity receiver (DRx) configuration 200including a DRx front-end module (FEM) 208. It is to be understood thatthe features of the DRx FEM 208 can be implemented in any front-endmodule described herein, such as the RF module 106 described herein withreference to FIG. 1. The DRx configuration 200 includes a diversityantenna 170 that is configured to receive a diversity signal and providethe diversity signal to the DRx FEM 208 through a filter assembly 272.The filter assembly 272 can include a multiplexer, for example, that isconfigured to selectively direct signals within targeted frequencyranges along respective paths to an amplifier 210 having a multi-inputstage 212 that is coupled to amplifier architectures 220 that include alow NF core 222 and a high linearity core 224. The signals can be radiofrequency (RF) signals that include, for example and without limitation,cellular signals (e.g., low-, mid-, high- and/or ultra-high-bandcellular frequencies), WLAN signals, BLUETOOTH® signals, GPS signals,and the like.

The DRx FEM 208 is configured to perform processing on the diversitysignals received from the filter assembly 272. For example, the DRx FEM208 may be configured to filter the diversity signals to one or moreactive frequency bands that can include cellular and/or WLAN frequencybands. The controller 102 can be configured to control the DRx FEM 208to selectively direct signals to targeted filters to accomplish thefiltering. As another example, the DRx FEM 208 may be configured toamplify one or more of the filtered signals using a particular activecore 222, 224 of the amplifier architectures 220. To that end, the DRxFEM 208 may include filters, low-noise amplifiers, band select switches,matching circuits, and other components. The controller 102 can beconfigured to interact with components in the DRx FEM 208 tointelligently select paths for the signals through the DRx FEM 208.

The DRx FEM 208 transmits at least a portion of the processed diversitysignals to the transceiver 104. The transceiver 104 may be controlled bythe controller 102. In some implementations, the controller 102 may beimplemented within the transceiver 104.

The DRx FEM 208 can be configured to provide a plurality of gain modes.For the plurality of gain modes, different amplifier architectures 220can be selected to amplify input signals. In one or more gain modes, thesignals can be routed to a low NF core 222 to amplify signals with anemphasis on achieving a low NF, such as for high gain modes. In one ormore gain modes, the signals can be routed to a high linearity core 224to amplify signals with an emphasis on achieving a targeted linearity,such as for low or medium gain modes. It is to be understood thatdifferent amplifier architectures may also be implemented that providetargeted performance characteristics including, for example and withoutlimitation, NF, linearity, gain, bandwidth, power consumption,stability, input or output matching, reverse isolation, or anycombination of these. Such amplifier architectures may be implemented inplace of or in addition to the amplifier architectures described herein.

In some embodiments, the amplifier architectures 220 include selectableimpedances coupled to the amplification stage to provide improvedimpedance matching, linearity, and/or IIP3. In some embodiments, the DRxconfiguration 200 is configured to bypass amplification when operatingin a low gain mode and to amplify signals with a particular amplifierarchitecture 220 when operating in other gain modes. This canadvantageously allow the DRx configuration 200 to improve linearityand/or NF in particular gain modes.

In some embodiments, the amplifier 210 is configured to receive aplurality of input signals and to provide a single output signal. Incertain embodiments, the amplifier 210 can be configured to receive aplurality of input signals and provide a corresponding plurality ofoutput signals. The filter assembly 272 can be configured to directsignals corresponding to particular frequency bands along designatedpaths to the amplifier 210. The amplifier 210 can provide different gainmodes for the received signals. The amplifier architectures 220 canprovide different amplification characteristics so that different gainmodes can be amplified using particular amplifier architectures toachieve desired or targeted amplification performance. The particularamplifier architecture that is selected, such as the low NF core 222 orthe high linearity core 224, can be based on the gain mode of theamplifier 210. In certain implementations, the amplifier 210 can operatein a bypass configuration such that the signal passes through a bypasspath 240 and in an amplification configuration such that the signalpasses through an amplification path that includes a selected amplifierarchitecture, such as low NF core 222 or high linearity core 224. Thiscan advantageously allow the DRx FEM 208 to provide variable gain and/ora plurality of gain modes while reducing the negative impacts onlinearity (e.g., IIP3) and/or noise factor (NF) relative toconfigurations that do not selectively provide amplifier architecturesfor particular gain modes. The amplifier 210 can include any suitableamplifier circuit configured to provide a desired or targetedamplification. In some embodiments, the amplifier 210 includes alow-noise amplifier (LNA) circuit configured to amplify signals from aplurality of frequency bands (e.g., cellular frequency bands and/or WLANfrequency bands) received at a plurality of inputs, or a multi-inputLNA. However, it is to be understood that the embodiments describedherein are not to be limited to implementations that utilize low-noiseamplifiers but include implementations that use any of a variety ofamplifiers.

The amplifier 210 can be configured to amplify signals based at least inpart on a plurality of gain modes. For example, the amplifier 210 can beconfigured to provide a first amplification or gain for a first gainmode, a second amplification or gain for a second gain mode, and so on.The amplifier 210 can be controlled by the controller 102 to control thegain provided at the amplifier 210. For example, the controller 102 canprovide a signal indicative of a desired or targeted gain to theamplifier 210 and the amplifier 210 can provide the targeted gain. Thecontroller 102 may receive an indication of the targeted gain fromanother component in a wireless device, for example, and control theamplifier 210 based at least in part on that indication. Similarly, theamplifier architectures 220 can be activated based at least in part on again mode and/or targeted gain of the amplifier 210.

The controller 102 can be configured to control the DRx FEM 208 toselectively provide tailored gain performance. For example, thecontroller 102 and the DRx FEM 208 can control the amplifierarchitectures 220 to direct signals to a targeted amplifier core (e.g.,low NF core 222 or high linearity core 224) based at least in part on again mode. As another example, the controller 102 and the DRx FEM 208can control the amplifier 210 to provide a bypass path 240 based atleast in part on a gain mode. As another example, the controller 102 andthe DRx FEM 208 can use the amplifier 210 to provide a plurality of gainmodes.

Example Architectures of Variable Gain Amplifiers

Front-end modules generally include amplifiers such as low-noiseamplifiers (LNAs) to amplify received signals. In wireless devices thatprovide a variety of gain modes, it may be advantageous to selectivelydirect signals through amplifier cores that provide targeted performancecharacteristics, such as low NF and/or high linearity, to improve oroptimize amplifier performance. Similarly, for at least one gain mode,it may be advantageous to bypass a gain stage to improve performance(e.g., linearity).

Accordingly, provided herein are variable gain amplifiers thatselectively direct signals to particular amplifier architecturesdepending at least in part on a gain mode of the variable gainamplifier. This advantageously reduces or eliminates performancepenalties in one or more gain modes. Similarly, this advantageouslyincreases or optimizes performance characteristics in one or more gainmodes. Furthermore, the amplifier architectures can be configured toimprove NF and/or linearity of the amplification process in targetedgain modes. Similarly, the variable gain amplifier can be configured toprovide a low-loss bypass mode in a low gain mode to improve signalquality.

FIG. 3A illustrates an example variable gain amplifier configuration 310a that includes a switchable reference bias 315, a gain mode selector321, a bypass block 340, and a plurality of amplifier architectures 320configured to receive input signals and to selectively amplify thereceived signals with a selected amplifier architecture 320 or toprovide a bypass path through the bypass block 340. Each of theamplifier architectures 320 is coupled to a degeneration switching block330 that is configured to selectively provide tailored impedances basedat least in part on a gain mode of the variable gain amplifierconfiguration 310 a. The gain mode selector 321 is configured to directsignals to a selected amplifier architecture 320 (e.g., a high gainstage 322 or a low gain stage 324) or to the bypass block 340 based atleast in part on a gain mode of the amplifier configuration 310 a. Thegain mode selector 321 includes elements that can switch the signal pathfrom the input to the targeted destination (e.g., a selected amplifierarchitecture 322 or 324 or the bypass block 340).

The amplifier architectures 320 include a high gain stage 322 and a lowgain stage 324. Each of the high gain stage 322 and the low gain stage324 can be configured to enhance or emphasize desired performancecharacteristics, where one or more of the enhanced characteristics canbe shared between the gain stages 322, 324 or they can be configured toenhance different characteristics. In some implementations, enhancementof certain performance characteristics may degrade other performancecharacteristics. However, this may be beneficial where, in a particulargain mode, the enhanced characteristics positively affect amplifierperformance more than the degraded characteristics negatively affectamplifier performance. For example, when operating in one or more highgain modes, the gain mode selector 321 can direct signals received fromthe input to the high gain stage 322. The high gain stage 322 can beconfigured to reduce NF relative to the low gain stage 324. In a highgain mode, smaller signals are typically received and may be moresusceptible to degradation due to noise. Hence, it may be beneficial totailor the amplifier so that it reduces the NF during amplification.Similarly, when operating in one or more low gain modes, the gain modeselector 321 can direct signals received from the input to the low gainstage 324. The low gain stage 324 can be configured to enhance or boostlinearity relative to the high gain stage 322. In a low gain mode,signals are typically larger and less susceptible to noise. Hence, itmay be more advantageous to tailor the amplifier so that it enhanceslinearity than to reduce noise. Accordingly, providing differentamplifier architectures for different gain modes allows signals to bedirected to advantageous amplifier architectures to achieve desired ortargeted performance characteristics.

The switchable reference bias 315 can be configured to provide referencebias voltages to the amplifier architectures 320. The reference biasvoltages can be configured to be tailored for a particular gain stage.For example, in one or more high gain modes, the switchable referencebias 315 can provide a first reference bias voltage to the high gainstage 322, and in one or more low gain modes, the switchable referencebias 315 can provide a second reference bias voltage to the low gainstage 324. In this way, the amplifier configuration 310 a can beconfigured to achieve desired or targeted bias current matching.

The variable gain amplifier configuration 310 a can be furtherconfigured to achieve targeted performance characteristics (e.g.,relatively high linearity, impedance matching, etc.) through the use ofthe degeneration switching block 330. In certain implementations, thebypass block 340 includes a shunt switch that can provide high input tooutput isolation relative to configurations without such a switch. Thevariable gain amplifier configuration 310 a can be configured to providea low-loss direct bypass mode by directing signals from the inputthrough the bypass block 340 and not through the amplifier architectures320. The low-loss direct bypass mode can be implemented in a low gainmode, for example. In some embodiments, the variable gain amplifierconfiguration 310 a can include a degeneration switching block 330 foreach input to further isolate the inputs.

The degeneration switching block 330 is configured to provide impedanceto the selected amplifier architecture 320. This can improve performanceby providing power and/or noise matching with prior stages in theprocessing chain. The degeneration switching block 330 can be configuredto improve performance (e.g., linearity and/or NF) of the amplifierarchitectures 320 by providing a feedback mechanism. In someembodiments, the degeneration switching block 330 is configured toprovide a first impedance for a first gain mode and a second impedancefor a second gain mode. The selected impedances provided by thedegeneration switching block 330 can also be configured to improvelinearity of the selected amplifier architecture 320. The variable gainamplifier configuration 310 a can be configured to bypass thedegeneration switching block 330 in a bypass mode. This can improvelinearity performance by reducing or minimizing leakage current passingthrough the selected amplifier architecture 320.

The bypass block 340 is configured to receive signals from the gain modeselector 321 and to provide a path to the output that does not passthrough the amplifier architectures 320 or the degeneration switchingblock 330. The bypass block 340 can include components that serve toisolate the input and output in one or more of the gain modes providedby the variable gain amplifier configuration 310 a.

The bypass switch 350 is configured to selectively provide a path fromthe input through the bypass block 340 to the output or a path from theinput through a selected amplifier architecture 320 to the output. Thebypass switch 350 can include one or more switching elements to isolateand/or to select the desired path based at least in part on a gain modeof the variable gain amplifier configuration 310 a.

In certain embodiments, the variable gain amplifier configuration 310 acan be configured to provide a plurality of gain modes, e.g., gain modesG0, G1, . . . , GN with G0 being the highest gain and GN being a bypassmode. When operating in gain mode GN, the variable gain amplifierconfiguration 310 a can be configured to direct signals from the inputto the bypass block 340. When operating in gain modes G0 to GN−1, thevariable gain amplifier configuration 310 a can be configured to directsignals through a selected gain stage 322, 324 and to activate thedegeneration switching block 330. The degeneration switching block 330can be configured to provide different impedance levels for individualgain modes or for groups of gain modes. Even in these gain modes, thebypass block 340 may be at least partially activated by activating ashunt switch in the bypass block 340 to provide isolation between theinputs and the output.

The variable gain amplifier configuration 310 a can be configured toactivate the high gain stage 322 for one or more of the gain modes G0 toGN−2 and to activate the low gain stage 324 for one or more of the gainmodes G1 to GN−1. In certain implementations, signals are directed tothe high gain stage 322 in gain mode G0 and signals are directed to thelow gain stage 324 in gain mode GN−1. For gain modes G1 to GN−2, signalsmay be directed to either the high gain stage 322 or to the low gainstage 324. In some embodiments, the amplifier configuration 310 a can bedynamically configured to direct signals to either the high gain stage322 or the low gain stage 324 regardless of the gain mode. In someembodiments, the amplifier configuration 310 a can operate in aparticular gain mode and can dynamically direct signals to the high gainstage 322 during a first time period and to the low gain stage 324during a second time period.

The variable gain signal amplifier configuration 310 a can be configuredto achieve relatively low noise and high linearity (e.g., higher IIP3)relative to amplifiers with a single amplifier architecture or core.Similarly, the variable gain signal amplifier configuration 310 a canachieve superior performance characteristics relative to amplifierswithout multiple amplifier architectures 320, bypass block 340, and/ordegeneration switching block 330. The variable gain signal amplifierconfiguration 310 a can be configured to amplify radio frequency (RF)signals such as cellular signals, WLAN signals, BLUETOOTH® signals, GPSsignals, and the like. The variable gain signal amplifier configuration310 a can be configured to provide broadband capabilities by receivingsignals over a plurality of frequency bands at the multiple inputs andprocessing these signals. The variable gain signal amplifierconfiguration 310 a can be configured to be controlled by a controlcircuit assembly, such as a controller (e.g., the controller 102described herein with reference to FIGS. 1 and 2). The control circuitassembly can intelligently and selectively switch paths betweenamplifier architectures 320 and a bypass path and can selectivelyprovide impedances with the degeneration switching block 330.

FIG. 3B illustrates another example variable gain amplifierconfiguration 310 b that includes the same components as the variablegain amplifier configuration 310 a of FIG. 3A, with an additionaldegeneration switching block 330 b. Thus, the variable gain amplifierconfiguration 310 b includes degeneration switching blocks 330 a and 330b respectively operating with the high gain stage 322 and the low gainstage 324. In some implementations, each gain stage of the amplifierarchitectures 320 includes a degeneration switching block or adegeneration element (e.g., inductive degeneration).

FIG. 3C illustrates another example variable gain amplifierconfiguration 310 c that includes the same components as the variablegain amplifier configuration 310 a of FIG. 3A, with multiple inputs,thereby providing a multi-input multi-gain amplifier with switchableactive cores. In certain implementations, the amplifier configuration310 c is configured to receive multiple signals at distinct input ports,each distinct input port configured to receive signals at one or moreparticular cellular frequency bands. For example, a signal in a firstband can be received at a first input port, a signal in a second bandcan be received at a second input port, and a signal in a third band canbe received at a third input port. The variable gain amplifierconfiguration 310 c can be configured to provide multi-input processingwithout the use of a switching network. The variable gain signalamplifier configuration 310 c can be configured to independently processsignals at the respective inputs.

It is to be understood that although three inputs are illustrated, thevariable gain amplifier configuration 310 c can include any suitablenumber of inputs. For example, and without limitation, the variable gainamplifier configuration 310 c can include at least 2 inputs, at least 4inputs, at least 8 inputs, at least 16 inputs, at least 32 inputs, atleast 64 inputs, or at least any number of inputs in the describedranges. As another example and without limitation, the variable gainamplifier configuration 310 c can include less than or equal to 64inputs, less than or equal to 32 inputs, less than or equal to 16inputs, less than or equal to 8, less than or equal to 4 inputs, or lessthan or equal to any number of inputs in the described ranges.

FIG. 3D illustrates another example variable gain amplifierconfiguration 310 d that includes the same components as the variablegain amplifier configuration 310 b of FIG. 3B, with multiple inputs,thereby providing a multi-input multi-gain amplifier with switchableactive cores and degeneration switching blocks for individual gainstages. Thus, the variable gain amplifier configuration 310 d includesdegeneration switching blocks 330 a and 330 b respectively operatingwith the high gain stage 322 and the low gain stage 324. In someimplementations, each gain stage of the amplifier architectures 320includes a degeneration switching block or a degeneration element (e.g.,inductive degeneration). In addition, certain implementations of theamplifier configuration 310 d are configured to receive multiple signalsat distinct input ports, each distinct input port configured to receivesignals at one or more particular cellular frequency bands. The variablegain amplifier configuration 310 d can be configured to providemulti-input processing without the use of a switching network. Thevariable gain signal amplifier configuration 310 d can be configured toindependently process signals at the respective inputs.

FIG. 3E illustrates another example variable gain amplifierconfiguration 310 d that includes the same components as the variablegain amplifier configuration 310 c of FIG. 3C, with additionalcomponents. For example, the variable gain amplifier configuration 310 dincludes matching networks 318 and 345. The output matching network 318is configured to provide impedance matching for an output load 316 andthe amplifier comprising the amplifier architectures 320 and a cascodebuffer 314. The bypass matching network 345 similarly provides impedancematching for the bypass block 340. For the matching networks 318 and345, any suitable combination of inductors and capacitors can be used toprovide the targeted impedances.

The variable gain amplifier configuration 310 d also includes the outputload 316 and cascode buffer 314 as part of the amplification chain. Thecascode buffer 314 can be configured to act as a current buffer. Thecascode buffer 314 is configured to provide isolation between theamplifier architectures 320 and the output. The cascode buffer 314 canalso be configured to improve the gain of the active cores 320 of thevariable gain amplifier configuration 310 d. The output load 316 isconfigured to provide a load to current to generate an output voltageswing. The output load 316 can be configured to be tuned or tunable foreach band received at the inputs. The output load 316 can be configuredto improve return loss and/or increase bandwidth by tailoring theresistance of the output load 316. The current through the output load316 can be used to set the gain mode of the variable gain amplifierconfiguration 310 d. For example, a lower current flowing through theoutput load 316 can be configured to correspond to a lower gain of thevariable gain amplifier configuration 310 d.

FIG. 3F illustrates another example variable gain amplifierconfiguration 310 f that includes the same components as the variablegain amplifier configuration 310 e of FIG. 3E, with an additionaldegeneration switching block 330 b as in the variable gain amplifierconfiguration 310 b or 310 d of FIGS. 3B and 3D, respectively. Thus, thevariable gain amplifier configuration 310 b includes degenerationswitching blocks 330 a and 330 b respectively operating with the highgain stage 322 and the low gain stage 324. In some implementations, eachgain stage of the amplifier architectures 320 includes a degenerationswitching block or a degeneration element (e.g., inductivedegeneration).

FIG. 4 illustrates a variable-gain signal amplifier 410 that includes aplurality of active cores 422, 424 in a variable-gain stage 420configured to receive an input signal and to generate an amplifiedoutput signal. The amplifier 410 can direct signals to the first activecore 422 or to the second active core using a gain mode selector 421,represented as a switch. It should be understood, however, that anycombination of electronic elements can be used as the gain mode selector421 to selectively direct signals to a particular active core. The firstactive core 422 can be configured to amplify signals while providingenhanced performance characteristics, such as low NF. The first activecore 422 can be used in one or more gain modes of the amplifier 410. Thesecond active core 424 can be configured to amplify signals whileproviding different or overlapping enhanced performance characteristicsrelative to the first active core 422, such as high linearity.

The active cores 422, 424 can be operated independently of one another.The active cores 422, 424 advantageously allow individual cores to betailored or optimized for one or more gain modes to improve overallperformance of the amplifier 410 across gain modes. Such amplifiers 410with independent active cores 422, 424 can advantageously allow for easymapping of particular gain modes to one of the active cores. If it isdesirable to achieve different performance characteristics for aparticular gain mode, it is not necessary to redesign the amplifier 410because an individual core can be modified without affecting all gainmodes (e.g., gain modes mapped to other active cores). This allows fortargeted tuning for particular gain modes. This also allows for dynamicand independent assignment of gain modes to active cores. This alsoallows particular active cores to be tailored or optimized to satisfyparticular performance requirements. For example, in a high gain mode,reducing NF may be of particular interest, so an active core can bedesigned to reduce NF while other performance characteristics may bedegraded. Similarly, in medium or low gain modes, linearity may be ofparticular interest, so an active core can be designed to enhancelinearity while other performance characteristics may be degraded orgain may be decreased. As another example, the active core configuredfor use in medium or low gain modes can be a different size from anactive core configured for use in a high gain mode. Accordingly,different active cores can be of different sizes, types, etc.

In some embodiments, the amplifier 410 can include 3 or more activecores, 4 or more active cores, or 5 or more active cores. In variousembodiments, the amplifier 410 can include less than or equal to 10active cores, less than or equal to 7 active cores, or less than orequal to 5 active cores. In a first gain mode, the amplifier 410 candirect signals through an amplification path that includes the firstactive core 422. In a second gain mode, the amplifier 410 can directsignals through an amplification path that includes the second activecore 424. In some embodiments, the amplifier 410 can direct signals tothe first active core 422 for a plurality of gain modes. In certainembodiments, the amplifier 410 can direct signals to the second activecore 424 for a plurality of gain modes. In various embodiments, thefirst active core 422 provides higher gain than the second active core424. In certain embodiments, the second active core 424 provides lowergain and higher linearity than the first active core 422.

FIG. 5 illustrates a variable-gain signal amplifier 510 that includes aswitchable reference bias 515 coupled to the active cores 522, 524 ofthe variable-gain stage 520. The switchable reference bias 515 canselectively provide reference bias signals to the active core that hasbeen selected based on the gain mode of the amplifier 510. Theswitchable reference bias 515 can be configured to provide currentmatching in the selected active core of the gain stage 520.

FIG. 6 illustrates a variable-gain signal amplifier 610 that includes abypass block 640 that provides a bypass path in addition to theamplification path through one of the active cores 422, 424 of thevariable-gain stage 420. The amplifier 610 has a gain mode selector thatincludes a bypass switch 621 b and a core switch 621 a. The bypassswitch 621 b directs signals to the bypass block 640 in a bypass mode.The bypass switch 621 b directs signals to the core switch 621 a in anamplification mode. The core switch 621 a directs signals to aparticular active core 422, 424 depending on the gain mode of theamplifier 610. In some embodiments, the gain mode selector includes asingle-pole, multi-throw switch configuration to direct signals to theappropriate destination (e.g., the bypass block 640, the first activecore 422, or the second active core 424). In some embodiments, the gainmode selector includes a combination of switches or transistors or othersimilar components to accomplish the selective directing of inputsignals along targeted paths.

FIG. 7 illustrates a variable-gain signal amplifier 710 that includes adegeneration switching block 730 coupled to active cores 722, 724 of thevariable-gain stage 720. The degeneration switching block 730 can beconfigured to provide a plurality of inductances for different gainlevels of the variable-gain stage 720. The degeneration switching block730 can be configured to provide various impedance values associatedwith the various gain levels. The degeneration switching block 730 iscoupled to the active cores 722, 724 and can be implemented as part ofone of the cores, such as the second active core 724. In someimplementations, each active core has a degeneration component, such asan inductive degeneration or a degeneration switching circuit.

FIGS. 8A and 8B illustrate an example variable gain amplifierconfiguration 810 that is configured similarly to the variable gainamplifier 310 d described herein with reference to FIG. 3E. The variablegain amplifier 810 includes example electrical components to demonstratean example implementation of the amplifier 810. It is to be understood,however, that this is merely an illustrative example implementation andthe scope of the disclosure extends to additional implementationsencompassing similar architectures.

The variable gain amplifier configuration 810 includes a first activecore 822, a second active core 824, and a bypass block 840. Signals arereceived at inputs A and B and, depending on the gain mode, directedthrough the first active core 822, the second active core 824, or thebypass block 840 to the output. In some embodiments, the first activecore 822 is configured to amplify signals in a high gain mode or in aplurality of high gain modes, the first active core 822 configured toreduce NF relative to the second active core. In some embodiments, thesecond active core 824 is configured to amplify signals in a low gainmode or in a plurality of low gain modes, the second active core 824configured to enhance linearity or improve IIP3 relative to the firstactive core 822. The bypass block 840 is configured to provide signals abypass path in a lowest gain mode. In some embodiments, the first activecore 822 can be referred to as a high gain core or a low NF core. Insome embodiments, the second active core 824 can be referred to as alinearity boost core, a medium gain core, or a low gain core.

The first active core 822 includes a multi-input gain stage 812configured to receive inputs A and B and to selectively amplify thereceived signals with corresponding transistors Q1 and Q2 in conjunctionwith corresponding transistors Q3 and Q4 and a cascode buffer 814 a withthe transistor Q5. The first active core 822 includes feedback caps 817a, 817 b coupled between the output and inputs A and B, respectively.The variable capacitor can be tuned to improve IIP3 linearity and/or tomatch input impedance. The feedback caps 817 a, 817 b are configured toprovide a way to control linearity of the amplification process. Thefeedback caps 817 a, 817 b are also configured to provide a targetedinput impedance.

The multi-input gain stage 812 provides a voltage to current gain stagecomprising the transistors Q1 and Q2. Further, the multi-input gainstage 812 is configured to amplify respective input signals inconjunction with transistors Q3 and Q4 and the cascode buffer 814 a thatacts as a current buffer to lower input impedance and to increase outputimpedance.

The first active core 822 includes isolation switch 813, having switchS5, configured to isolate input to the first active core 822 from thesecond active core 824 when the first active core 822 is active and toisolate input to the bypass block 840 from the second active core 824when operating in a bypass mode. In other words, switch S5 in theisolation switch 813 is open when the second active core 824 is activeand closed during other operating modes (e.g., other gain modes orbypass mode). The amplifier configuration 810 also includes a similarbypass isolation switch 844, having switch S6, in the bypass block 840to isolate input to the first active core 822 and the second active core824 from the bypass block 840. In other words, switch S6 in the bypassisolation switch 844 is open when operating in bypass mode and closedduring other operating modes (e.g., other gain modes).

The first active core 822 includes switches to selectively directsignals to the second active core 824 rather than through the firstactive core 822. It is to be understood that although the switches areshown as part of the first active core, these switching elements can beimplemented in any part of the amplifier configuration 810. Switches S1and S4 respectively direct input signals from inputs A and B to thebypass block 840. Switches S2 and S3 respectively direct input signalsfrom inputs A and B to the second active core 824 through the point C.The switches S1-S4 can be implemented using any suitable switchingcomponents, such as switches, transistors, or the like. The switchesS1-S4 can be operated based at least in part on the gain mode of theamplifier configuration 810. For example, in a high gain mode, theswitches S1-S4 can be open to direct signals from inputs A or B throughthe first active core. In one or more other gain modes, the switches S2or S3 can be closed (with the remaining switches open) to direct signalsthrough the second active core 824. In a bypass mode or in a lowest gainmode, the switches S1 or S4 can be closed (with the remaining switchesopen) to direct signals along a bypass path through the bypass block840.

Similar to the first active core 822, the second active core 824 has anamplification chain that includes a transistor Q6 and a cascode buffer814 b with the transistor Q7. The gate voltages can be different fordifferent cascode buffers 814 a, 814 b in the different active cores822, 824. Linearity depends at least in part on how the cascode buffers814 a, 814 b are biased. This provides an additional method of tuningperformance of the active cores 822, 824, e.g., to enhance linearity inthe second active core 824 relative to the first active core 822.

The second active core 824 includes a feedback cap 817 c coupled to thepoint C, or the input to the second active core 824 from input A orinput B. The feedback cap 817 c is configured to provide a way tocontrol linearity of the amplification process and to provide a targetedinput impedance.

The second active core 824 includes a degeneration switching block 830that is configured to selectively provide tailored impedances based atleast in part on a gain mode of the variable gain amplifierconfiguration 810. The degeneration switching block 830 is also coupledto the amplification path of the first active core 822 at point E. Inthis way, the first active core 822 and the second active core 824 sharethe degeneration switching block 830. In certain implementations, themulti-input gain stage 812 is configured to receive multiple signals atdistinct input ports, each distinct input port configured to receivesignals at one or more particular cellular frequency bands. For example,input A receives a signal in a first band and input B receives a signalin a second band. In some embodiments, each of the transistors Q1, Q2,and Q6 can be coupled to a dedicated degeneration switching block 830 toincrease isolation between input ports.

The degeneration switching block 830 is configured to provide impedanceto the gain stage of the multi-input gain stage 812 of the first activecore 822 or the transistor Q6 of the second active core 824. This canimprove performance by providing power and/or noise matching with priorstages in the processing chain. The degeneration switching block 830 canbe configured to improve linearity of the gain stage (e.g., transistorsQ1, Q2, or Q6) by providing a feedback mechanism. The degenerationswitching block 830 can be configured to provide a first impedance L1for a first gain mode and a second impedance provided by L1 and L2 for asecond gain mode by respectively activating the transistor M1 and thetransistor M2. The selected impedances provided by the degenerationswitching block 830 can also be configured to improve linearity of thegain stage. In a bypass mode, the transistors M1 and M2 can be off. Thevariable gain amplifier configuration 810 can be configured to bypassthe first active core 822 and the second active core 824 in a bypassmode. This can improve linearity performance by reducing or minimizingleakage current passing through the respective active cores 822, 824. Incertain implementations, the degeneration switching block 830 can beconfigured to provide a lower inductance for higher gain modes. Theamount of inductance provided by the degeneration switching block 830can change with changes in gain mode of the variable gain amplifierconfiguration 810.

The degeneration switching block 830 can be configured to changeinductance to increase performance of the variable gain amplifier 810relative to an amplifier with fixed inductance. Performance can beincreased by increasing linearity and/or by reducing noise introducedduring amplification, for example.

The bypass block 840 is configured to receive signals from the multipleinputs and to provide a path to the output that does not pass throughthe first active core 822 or the second active core 824. The bypassblock 840 is configured to provide a path to the output through tunablematching network 845, similar to the matching network 345 describedherein with reference to FIG. 3E. The bypass block 840 can be configuredto provide two paths to the output, a direct path and an output tankpath, activated by closing switch S7. The output tank path is directedto a path that is coupled to an output load 816 at point D, the outputload similar to the output load 316 described herein with reference toFIG. 3E. The bypass block 840 also includes a bypass isolation switch844, or shunt switch, that selectively couples the bypass block 840 to areference potential node to aid in isolating the inputs from the output.The bypass matching network 845 can provide additional impedancematching flexibility.

The variable gain amplifier configuration 810 can be configured toprovide multi-input processing without the use of a switching network.The variable gain amplifier configuration 810 can be configured toachieve relatively high linearity through the use of the degenerationswitching block 830. The variable gain amplifier configuration 810 canbe configured to provide a low-loss direct bypass mode by directingsignals from the inputs through the bypass block 840. The low-lossdirect bypass mode can be implemented in a low gain mode, for example.

The amplifier configuration 810 includes a bypass switch 850 that isconfigured to selectively provide a path from input A or input B throughthe bypass block 840 to the output or a path from input A or input Bthrough one of the active cores 822, 824 to the output. The bypassswitch 850 includes switches S8 and S9 that respectively controlconnection of a bypass path to the output and an amplification path tothe output. The bypass switch 850 can be controlled based at least inpart on a gain mode of the variable gain amplifier 810.

The matching networks 818 and 845 can include any suitable combinationof inductors and capacitors that can be used to provide targetedimpedances. The output matching network 818 is configured to provideimpedance matching for an output load 816 and the active cores 822, 824.The bypass matching network 845 similarly provides impedance matchingfor the bypass block 840.

The variable gain amplifier 810 includes the output load 816 and cascodebuffers 814 a, 814 b as part of the amplification path. The cascodebuffers 814 a, 814 b includes respective transistors Q5 and Q7 that areconfigured to act as current buffers. The cascode buffers 814 a, 814 bare configured to provide isolation between the gain stages of therespective active cores 822, 824 and the output. The cascode buffers 814a, 814 b can also be configured to provide a targeted gain for therespective active cores 822, 824. The output load 816 is configured toprovide a load to current to generate an output voltage swing. Theoutput load 816 can be configured to be tuned or tunable for each bandreceived at the inputs. For example, the output load 816 includes avariable capacitor C1 that can be tuned for particular cellularfrequency bands. The output load 816 can also be configured to improvereturn loss and/or increase bandwidth by tailoring the resistance R1 ofthe output load 816.

FIG. 8B illustrates a switchable reference bias circuit 815 used inconjunction with the amplifier configuration 810 of FIG. 8A. Theswitchable reference bias circuit 815 is coupled to the amplifierconfiguration 810 of FIG. 8A at points A and B. The switchable referencebias circuit 815 includes a power supply voltage, V_(DD), and a currentsource, I_(DD). The current is selectively directed through transistorsQ1-Q4 through the use of switches S1-S8. This can be used to providetargeted current matching for the active cores 822, 824. For example,switches S2 and S3 can be closed and switches S1 and S4 can be openedwhen operating in a gain mode that uses the first active core 822 toamplify signals from input A. Similarly, switches S1 and S4 can beclosed and switches S2 and S3 can be opened when operating in a gainmode that uses the second active core 824 to amplify signals from inputA. Likewise, switches S6 and S7 can be closed and switches S5 and S8 canbe opened when operating in a gain mode that uses the first active core822 to amplify signals from input B. Similarly, switches S6 and S7 canbe closed and switches S5 and S8 can be opened when operating in a gainmode that uses the second active core 824 to amplify signals from inputB. In some embodiments, when amplifying signals from input A, switchesS5 and S6 are closed and switches S7 and S8 are opened to deactivatetransistors Q3 and Q4 in the switchable reference bias circuit 815.Similarly, when amplifying signals from input B, switches S1 and S2 areclosed and switches S3 and S4 are opened to deactivate transistors Q1and Q2. This can be extended to more than two inputs (e.g., inputs inaddition to input A and input B).

The switchable reference bias circuit 815 includes a resistor 881 abetween the point A in FIGS. 8A and 8B and the switch S4. Similarly, theswitchable reference bias circuit 815 includes a resistor 881 b betweenthe point B in FIGS. 8A and 8B and the switch S8. The resistors 881 a,881 b are configured to isolate the switchable reference bias circuit815 from the active amplification cores. The resistors 881 a, 881 b canbe configured to provide a relatively high RF impedance to theswitchable reference bias circuit 815 and/or to prevent or reduce noisefrom passing from the switchable reference bias circuit 815 to theactive amplification core 822, 824.

It is to be understood that although FIGS. 8A and 8B illustrate anamplifier configuration 810 having two inputs (inputs A and B), theamplifier configuration 810 can be configured to receive more than 2inputs, such as 3 or more inputs, 4 or more inputs, 5 or more inputs,etc.

FIG. 9A illustrates another example amplifier configuration 910 a thatis similar to the amplifier configuration 810 described herein withreference to FIGS. 8A and 8B. The difference between the amplifierconfiguration 910 a and the amplifier configuration 810, is that theamplifier configuration 910 a includes inductor L0 coupled to themulti-input gain stage 912 rather than coupling the multi-input gainstage to the degeneration switching block 930, as was done in theamplifier configuration 810. The inductor L0 can provide inductivedegeneration for the first active core 922 while the degenerationswitching block 930 can provide similar functionality, described herein,for the second active core 922. Thus, the amplifier configuration 910 ais configured to provide separate degeneration elements for each activecore 822, 824.

This may be extended to amplifier configurations having more than 2active cores. Configurations can also be implemented where 2 or moreactive cores share a degeneration switching circuit with 1 or moredifferent active cores including their own degeneration elements. Theinductors L0, L1, and L2 are configured to provide real impedance to theamplifier inputs. This may be beneficial for power and/or noise matchingwith prior stages in the amplification or signal processing chain.Furthermore, the inductors L0, L1, and L2 are configured to improvelinearity of the respective active cores by providing a series feedbackmechanism. For example, when high linearity is desirable, both L1 and L2can be activated.

FIG. 9B illustrates another example amplifier configuration 910 b thatadds some components to the amplifier configuration 910 a describedherein with reference to FIG. 9A. Relative to the amplifierconfiguration 910 a, the amplifier configuration 910 b includes avariable attenuator 925 in the second active core 924. The variableattenuator 925 can be selectively used to attenuate signals prior toamplification in the second active core 924. The variable attenuator 925can be activated to decrease signal levels, which can boost linearityand increase NF, however this increase in NF may be more tolerable inlower gain modes than in high gain modes.

The amplifier configuration 910 b also includes third-ordertransconductance cancellation blocks (or gm3 cancellation blocks) 927 a,927 b, 927 c included in the first active core 922 and the second activecore 924, respectively. In the first active core 922, the gm3cancellation block 927 a is coupled to the amplification path at pointF. In the second active core 924, the gm3 cancellation block 927 b iscoupled to the amplification path between transistor Q6 and the cascodebuffer 914 b, the gm3 cancellation block including a transistor with thegate coupled to the drain of transistor Q6, a drain coupled to the drainof the transistor Q7 of the cascode buffer, and a source coupled to thesource of the transistor Q6. The gm3 cancellation blocks 927 a, 927 b,927 c can be configured to further improve IIP3 linearity of therespective active cores 922, 924. The gm3 cancellation blocks 927 a, 927b, 927 c can be modular in that they can be selectively included in oneor more active cores. The gm3 cancellation blocks 927 a, 927 b, 927 cfunction to improve performance by injecting current with an oppositesign of the third-order transconductance current in the mainamplification paths (e.g., the transistors Q3, Q4, and Q6). The gm3cancellation blocks 927 a, 927 b, 927 c can include an active MOSFET,resistor, capacitor, or any combination of these and other components.In some embodiments, the point F can be coupled to the drain of Q1, tothe drain of Q2, and/or to the drain of Q6. In some embodiments, thepoint G can be removed so that there are two gm3 cancellation blocks 927a, 927 b. In some embodiments, the gm3 cancellation block 927 b can beimplemented in the first active core 922. In such embodiments, the gm3cancellation block 927 b can be coupled to the drain of Q1 and/or to thedrain of Q2 in a manner similar to how it is coupled to the drain of Q6in FIG. 9B. In some embodiments, the point G can be coupled to the drainof Q2 and/or to the drain of Q6.

FIGS. 10A-10E illustrate examples of operating modes of the variablegain signal amplifier configuration 910 a of FIG. 9A. FIGS. 10A and 10Billustrate operation in one or more high gain modes, which may also bereferred to as low NF modes, for amplifying signals from input A andinput B. In these high gain modes, the first active core 922 isactivated, the second active core 924 is deactivated, and the bypassblock 940 is deactivated, except for the bypass isolation switch 944(which is closed). In FIG. 10A, signals received at the input A aredirected through the multi-input gain stage 912 comprising transistorQ1, through transistor Q3, and through the cascode buffer 914 a to theoutput through the output matching network 918 and the bypass switch950. Similarly, signals received at the input B are directed through themulti-input gain stage 912 comprising transistor Q2, through transistorQ4, and through the cascode buffer 914 a to the output through theoutput matching network 918 and the bypass switch 950. The bypass switch950 closes switch S9 and opens switch S8 in these high gain modes. Forsignals from both input A and input B, the amplifier configuration 910 aprovides inductive degeneration to the gain stage through inductor L0.Switches S1-S4 are open so signals do not propagate to the second activecore 924 or the bypass block 940. Furthermore, isolation switch 913 isclosed to further isolate the inputs from the second active core 924. InFIG. 10B, the first active core 922 is activated to amplify signalsreceived at input A and input B, as in FIG. 10A, with feedback loopsactivated through feedback caps 917 a and 917 b.

FIGS. 10C and 10D illustrate operation in one or more medium gain modesfor amplifying signals from input A and input B. These modes may also bereferred to as low gain or high linearity modes. In these medium gainmodes, the first active core 922 is deactivated, the second active core924 is activated, and the bypass block 940 is deactivated, except forthe bypass isolation switch 944 (which is closed). In FIG. 10C, signalsreceived at input A are directed to the point C through closed switch S2(with switch S3 open). Similarly, signals received at input B aredirected to the point C through closed switch S3 (with switch S2 open).For signals received from input A or input B, the signals then passthrough gain stage transistor Q6 and cascode buffer 914 b to the outputthrough the output matching network 918 and the bypass switch 950. Thebypass switch 950 closes switch S9 and opens switch S8 in these mediumgain modes. Selective inductive degeneration is provided to the gainstage through the degeneration switching block 930. The degenerationswitching block can selectively activate transistor M2 (with M1activated) to provide a selected inductance to the second active core924. This allows the second active core 924 to increase impedance forlower gain modes, or, to decrease impedance for higher gain modes.Switches S1 and S4 are open so signals do not propagate to the bypassblock 940. Furthermore, isolation switch 913 is open to allow signals topropagate to the second active core 924. In FIG. 10D, the feedback cap917 c is activated to provide a feedback loop to the second active core924.

FIG. 10E illustrates operation in a low gain mode or a passive bypassmode for signals received from input A or input B. In the bypass mode,the bypass block 940 is activated and the active cores 922, 924 aredeactivated, except isolation switch 913 (which is closed). Signalsreceived at input A are directed through the bypass block 940 by closingswitch S1 and through the bypass matching network 945 and to the outputthrough the bypass switch 950 by opening switch S9 and closing switchS8. Signals received at input B are directed through the bypass block940 by closing switch S4 and through the bypass matching network 945 andto the output through the path coupled to the tunable output load 916 atpoint D, activated by closing switches S7 and S9 and opening switch S8.It should be noted that signals from input A can be routed to the outputthrough the path that includes point D, and that signals from input Bcan be routed to the output through the path that does not include pointD. Furthermore, the transistors M1 and M2 are off to deactivate thedegeneration switching block 930 to improve linearity performance byreducing or minimizing leakage current through the gain stagetransistors. In bypass mode for input A, switch S1 is closed withswitches S2, S3, and S4 open. In bypass mode for input B, switch S4 isclosed with switches S1, S2, and S3 open. The bypass isolation switch944 is deactivated in the bypass mode.

FIGS. 11A-11D illustrate operation of a switchable reference biascircuit 1115 in different gain modes for signals from input A or inputB. The switchable reference bias circuit 1115 is configured like theswitchable reference bias circuit 815 described herein with reference toFIG. 8B. FIG. 11A illustrates that, in one or more high gain modes, whenthe first active core is activated and signals are received at input Asuch as in FIG. 10A or FIG. 10B, switch S3 is closed to activatetransistor Q1 and switches S2, S5, and S6 are closed to respectivelydeactivate transistors Q2, Q3, and Q4, with the remaining switches S1,S4, S7, and S8 open. FIG. 11B illustrates that, in one or more high gainmodes, when the first active core is activated and signals are receivedat input B such as in FIG. 10A or FIG. 10B, switch S7 is closed toactivate transistor Q3 and switches S1, S2, and S6 are closed torespectively deactivate transistors Q1, Q2, and Q4, with the remainingswitches S3, S4, S5, and S8 open. FIG. 11C illustrates that, in one ormore medium or low gain modes, when the second active core is activatedand signals are received at input A such as in FIG. 10C or FIG. 10D,switch S4 is closed to activate transistor Q2 and switches S1, S5, andS6 are closed to respectively deactivate transistors Q1, Q3, and Q4,with the remaining switches S2, S3, S7, and S8 open. FIG. 11Dillustrates that, in one or more medium or low gain modes, when thesecond active core is activated and signals are received at input B suchas in FIG. 10C or FIG. 10D, switch S8 is closed to activate transistorQ4 and switches S1, S2, and S5 are closed to respectively deactivatetransistors Q1, Q2, and Q3, with the remaining switches S3, S4, S6, andS7 open.

Examples of Products and Architectures

FIG. 12 illustrates that in some embodiments, some or all of theamplifier configurations, including some or all of the amplifierconfigurations having the combinations of features described herein(e.g., FIGS. 1-11D), can be implemented, wholly or partially, in amodule. Such a module can be, for example, a front-end module (FEM).Such a module can be, for example, a diversity receiver (DRx) FEM. Sucha module can be, for example, a multi-input, multi-output (MiMo) module.

In the example of FIG. 12, a module 1206 can include a packagingsubstrate 1201, and a number of components can be mounted on such apackaging substrate 1201. For example, a controller 1202 (which mayinclude a front-end power management integrated circuit [FE-PIMC]), acombination assembly 1207, a variable gain amplifier assembly 1210 thatincludes switchable active cores 1220 having one or more features asdescribed herein, and a filter bank 1209 (which may include one or morebandpass filters) can be mounted and/or implemented on and/or within thepackaging substrate 1201. Other components, such as a number of SMTdevices 1205, can also be mounted on the packaging substrate 1201.Although all of the various components are depicted as being laid out onthe packaging substrate 1201, it will be understood that somecomponent(s) can be implemented over other component(s).

In some implementations, a device and/or a circuit having one or morefeatures described herein can be included in an RF electronic devicesuch as a wireless device. Such a device and/or a circuit can beimplemented directly in the wireless device, in a modular form asdescribed herein, or in some combination thereof. In some embodiments,such a wireless device can include, for example, a cellular phone, asmart-phone, a hand-held wireless device with or without phonefunctionality, a wireless tablet, etc.

FIG. 13 depicts an example wireless device 1300 having one or moreadvantageous features described herein. In the context of one or moremodules having one or more features as described herein, such modulescan be generally depicted by a dashed box 1306 (which can be implementedas, for example, a front-end module) and a diversity receiver (DRx)module 1308 (which can be implemented as, for example, a front-endmodule).

Referring to FIG. 13, power amplifiers (PAs) 1382 can receive theirrespective RF signals from a transceiver 1304 that can be configured andoperated to generate RF signals to be amplified and transmitted, and toprocess received signals. The transceiver 1304 is shown to interact witha baseband sub-system 1305 that is configured to provide conversionbetween data and/or voice signals suitable for a user and RF signalssuitable for the transceiver 1304. The transceiver 1304 can also be incommunication with a power management component 1307 that is configuredto manage power for the operation of the wireless device 1300. Suchpower management can also control operations of the baseband sub-system1305 and the modules 1306 and 1308.

The baseband sub-system 1305 is shown to be connected to a userinterface 1301 to facilitate various input and output of voice and/ordata provided to and received from the user. The baseband sub-system1305 can also be connected to a memory 1303 that is configured to storedata and/or instructions to facilitate the operation of the wirelessdevice, and/or to provide storage of information for the user.

In the example wireless device 1300, outputs of the PAs 1382 are shownto be matched (via respective match circuits 1384) and routed to theirrespective duplexers 1386. Such amplified and filtered signals can berouted to a primary antenna 1360 through a switching network 1309 fortransmission. In some embodiments, the duplexers 1386 can allow transmitand receive operations to be performed simultaneously using a commonantenna (e.g., primary antenna 1360). In FIG. 13, received signals areshown to be routed to a variable gain amplifier assembly 1310 a, whichprovides the features and benefits of the variable gain amplifiersdescribed herein. The DRx module 1308 includes a similar variable gainamplifier assembly 1310 b as well.

In the example wireless device 1300, signals received at the primaryantenna 1360 can be sent to a variable gain amplifier 1310 a in thefront-end module 1306. The variable gain amplifier 1310 a can includeswitchable active cores 1320. The variable gain amplifier 1310 a isconfigured to receive a plurality of signals at inputs 1311 and tooutput a plurality of processed signals at outputs 1319. The variablegain amplifier 1310 a is configured to amplify signals by directingsignals through a particular active core based at least in part on again mode. This can be done to improve NF for high gain modes and toimprove linearity for signals for medium and/or low gain modes relativeto variable gain amplifiers that do not include one or more of thedescribed features. In at least one low gain mode, the switchable activecores 1320 can be bypassed.

The wireless device also includes a diversity antenna 1370 and adiversity receiver module 1308 that receives signals from the diversityantenna 1370. The diversity receive module 1308 includes a variable gainamplifier 1310 b, similar to the variable gain amplifier 1310 a in thefront-end module 1306. The diversity receiver module 1308 and thevariable gain amplifier 1310 b process the received signals and transmitthe processed signals to the transceiver 1304. In some embodiments, adiplexer, triplexer, or other multiplexer or filter assembly can beincluded between the diversity antenna 1370 and the diversity receivermodule 1370, as described herein.

One or more features of the present disclosure can be implemented withvarious cellular frequency bands as described herein. Examples of suchbands are listed in Table 1. It will be understood that at least some ofthe bands can be divided into sub-bands. It will also be understood thatone or more features of the present disclosure can be implemented withfrequency ranges that do not have designations such as the examples ofTable 1. It is to be understood that the term radio frequency (RF) andradio frequency signals refers to signals that include at least thefrequencies listed in Table 1.

TABLE 1 Tx Frequency Rx Frequency Band Mode Range (MHz) Range (MHz) B1FDD 1,920-1,980 2,110-2,170 B2 FDD 1,850-1,910 1,930-1,990 B3 FDD1,710-1,785 1,805-1,880 B4 FDD 1,710-1,755 2,110-2,155 B5 FDD 824-849869-894 B6 FDD 830-840 875-885 B7 FDD 2,500-2,570 2,620-2,690 B8 FDD880-915 925-960 B9 FDD 1,749.9-1,784.9 1,844.9-1,879.9 B10 FDD1,710-1,770 2,110-2,170 B11 FDD 1,427.9-1,447.9 1,475.9-1,495.9 B12 FDD699-716 729-746 B13 FDD 777-787 746-756 B14 FDD 788-798 758-768 B15 FDD1,900-1,920 2,600-2,620 B16 FDD 2,010-2,025 2,585-2,600 B17 FDD 704-716734-746 B18 FDD 815-830 860-875 B19 FDD 830-845 875-890 B20 FDD 832-862791-821 B21 FDD 1,447.9-1,462.9 1,495.9-1,510.9 B22 FDD 3,410-3,4903,510-3,590 B23 FDD 2,000-2,020 2,180-2,200 B24 FDD 1,626.5-1,660.51,525-1,559 B25 FDD 1,850-1,915 1,930-1,995 B26 FDD 814-849 859-894 B27FDD 807-824 852-869 B28 FDD 703-748 758-803 B29 FDD N/A 716-728 B30 FDD2,305-2,315 2,350-2,360 B31 FDD 452.5-457.5 462.5-467.5 B32 FDD N/A1,452-1,496 B33 TDD 1,900-1,920 1,900-1,920 B34 TDD 2,010-2,0252,010-2,025 B35 TDD 1,850-1,910 1,850-1,910 B36 TDD 1,930-1,9901,930-1,990 B37 TDD 1,910-1,930 1,910-1,930 B38 TDD 2,570-2,6202,570-2,620 B39 TDD 1,880-1,920 1,880-1,920 B40 TDD 2,300-2,4002,300-2,400 B41 TDD 2,496-2,690 2,496-2,690 B42 TDD 3,400-3,6003,400-3,600 B43 TDD 3,600-3,800 3,600-3,800 B44 TDD 703-803 703-803 B45TDD 1,447-1,467 1,447-1,467 B46 TDD 5,150-5,925 5,150-5,925 B65 FDD1,920-2,010 2,110-2,200 B66 FDD 1,710-1,780 2,110-2,200 B67 FDD N/A738-758 B68 FDD 698-728 753-783

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense, as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” The word “coupled”, as generally usedherein, refers to two or more elements that may be either directlyconnected, or connected by way of one or more intermediate elements.Additionally, the words “herein,” “above,” “below,” and words of similarimport, when used in this application, shall refer to this applicationas a whole and not to any particular portions of this application. Wherethe context permits, words in the above Description using the singularor plural number may also include the plural or singular numberrespectively. The word “or” in reference to a list of two or more items,that word covers all of the following interpretations of the word: anyof the items in the list, all of the items in the list, and anycombination of the items in the list.

The above detailed description of embodiments of the invention is notintended to be exhaustive or to limit the invention to the precise formdisclosed above. While specific embodiments of, and examples for, theinvention are described above for illustrative purposes, variousequivalent modifications are possible within the scope of the invention,as those skilled in the relevant art will recognize. For example, whileprocesses or blocks are presented in a given order, alternativeembodiments may perform routines having steps, or employ systems havingblocks, in a different order, and some processes or blocks may bedeleted, moved, added, subdivided, combined, and/or modified. Each ofthese processes or blocks may be implemented in a variety of differentways. Also, while processes or blocks are at times shown as beingperformed in series, these processes or blocks may instead be performedin parallel, or may be performed at different times.

The teachings of the invention provided herein can be applied to othersystems, not necessarily the system described above. The elements andacts of the various embodiments described above can be combined toprovide further embodiments.

While some embodiments of the inventions have been described, theseembodiments have been presented by way of example only, and are notintended to limit the scope of the disclosure. Indeed, the novel methodsand systems described herein may be embodied in a variety of otherforms; furthermore, various omissions, substitutions and changes in theform of the methods and systems described herein may be made withoutdeparting from the spirit of the disclosure. The accompanying claims andtheir equivalents are intended to cover such forms or modifications aswould fall within the scope and spirit of the disclosure.

What is claimed is:
 1. A variable-gain signal amplifier configured toprovide a plurality of gain modes, the amplifier comprising: an inputnode configured to receive an input signal; an output node configured toprovide an amplified output signal; a first active core configured toreceive the input signal and to generate the amplified output signal forthe output node; a second active core configured to receive the inputsignal and to generate the amplified output signal for the output node;a switchable reference bias circuit configured to provide a firstreference bias current to the first active core in the first gain modeand a second reference bias current to the second active core in thesecond gain mode; and a gain mode selector configured to direct theinput signal to the first active core in a first gain mode and to directthe input signal to the second active core in a second gain modedifferent from the first gain mode.
 2. The amplifier of claim 1 whereinthe input signal comprises a radio frequency signal.
 3. The amplifier ofclaim 1 wherein the gain mode selector is configured to selectivelyprovide a bypass path that bypasses the first active core and the secondactive core and an amplification path that passes through either thefirst active core or the second active core.
 4. The amplifier of claim 1further comprising a degeneration switching block coupled to the firstactive core and to the second active core, the degeneration switchingblock configured to provide tailored impedances to the first active coreand to the second active core.
 5. The amplifier of claim 4 wherein thetailored impedances are configured to provide improved linearity in theamplified output signal relative to a variable gain stage that is notcoupled to the degeneration switching block with the tailoredimpedances.
 6. The amplifier of claim 4 wherein the degenerationswitching block is configured to provide a first tailored impedance forthe first gain mode and a second tailored impedance for the second gainmode.
 7. The amplifier of claim 6 wherein the first tailored impedanceis greater than the second tailored impedance and the first gain levelis less than the second gain level.
 8. The amplifier of claim 1 whereinthe first active core is configured to have a lower noise figure thanthe second active core.
 9. The amplifier of claim 8 wherein the secondactive core is configured to have a higher linearity than the firstactive core.
 10. The amplifier of claim 9 wherein the first gain mode ishigher than the second gain mode.
 11. The amplifier of claim 1 furthercomprising a plurality of input nodes.
 12. The amplifier of claim 11wherein the amplifier is configured to receive a plurality of inputsignals at the plurality of input nodes, individual received signalshaving frequencies within different signal frequency bands.
 13. Theamplifier of claim 12 wherein the amplifier is configured to amplifysignals received at individual input ports independent of amplificationof other received signals.
 14. The amplifier of claim 1 furthercomprising a bypass block coupled to the input node and configured to beactivated in a low gain mode to provide a bypass path that does notinclude the first active core and the second active core.
 15. Theamplifier of claim 1 wherein each of the first active core and thesecond active core include a cascode buffer coupled to an output of again stage.
 16. A front-end module comprising: a packaging substrate; avariable gain signal amplifier implemented on the packaging substrate,the variable gain signal amplifier including a first active coreconfigured to receive an input signal and to generate an amplifiedoutput signal, a second active core configured to receive the inputsignal and to generate the amplified output signal, a switchablereference bias circuit configured to provide independent bias currentsto the first active core and to the second active core, a gain modeselector configured to direct the input signal to the first active corein a first gain mode and to direct the input signal to the second activecore in a second gain mode, and a controller implemented to control thevariable gain signal amplifier to provide a plurality of gain modesincluding the first gain mode and the second gain mode.
 17. The moduleof claim 16 wherein the first active core is configured to have a lowernoise figure than the second active core and the second active core isconfigured to have a higher linearity than the first active core.
 18. Awireless device comprising: an antenna; a filter assembly coupled to theantenna to receive signals and to direct frequency bands along selectpaths; and a variable gain signal amplifier including a first activecore configured to receive an input signal and to generate an amplifiedoutput signal, a second active core configured to receive the inputsignal and to generate the amplified output signal, a switchablereference bias circuit configured to provide independent bias currentsto the first active core and to the second active core, and a gain modeselector configured to direct the input signal to the first active corein a first gain mode and to direct the input signal to the second activecore in a second gain mode; and a controller implemented to control thevariable gain signal amplifier to provide a plurality of gain modes. 19.The amplifier of claim 1 wherein the switchable reference bias circuitincludes a single voltage source, a single current source, and aplurality of switches to generate and to selectively direct the firstreference bias current to the first active core and to generate and toselectively direct the second reference bias current to the secondactive core.
 20. The module of claim 16 wherein the switchable referencebias circuit includes a single voltage source, a single current source,and a plurality of switches to generate and to selectively direct theindependent bias currents to the first active core and to the secondactive core.